• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.145-152
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• 1999

This paper presents the principle and experimental results of a non-contact surface roughness measurement by means of screen projected pattern of lase beam reflected from a polished surface. In the reflected laser beam pattern especially from a fine surface like ground or polished one, light intensity varies from the center fo the image to its boundary as the Gaussian distribution. The standard deviation of a light intensity distribution is assumed to be a good non-contact estimator for measuring the surface roughnes, because the light reflectivity is known to be well related with the surface roughness. This method doesn't need to discriminate between the specularly reflected light and the diffusely reflected one, whereas the scattered laser intensity method must do. Nor it needs to adjust the change of light intensity caused by environmental lights or specimen materials. Reflected laser beam pattern narrowly spreads out in the vertical direction to tiny scratches on the polished surface due to abrasives. The deeper the scratch the more the dispersion, which means the rougher surface. The standard deviation of the pattern is nearly in proportion to the surface roughness. Measurement errors by this method are shown to be below 10 percent compared with those obtained by a common contact method. The inclination of measuring unit from the normal axis causes the measurement errors up to 10 percent for an angle of 4 degree. Therefore the proposed method can be used as an on-the-machine quick roughness estimator within 10 percent measurement error.

• Journal of Korean Society of Steel Construction
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• v.29 no.6
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• pp.401-410
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• 2017

This study deals with dynamic instability of a tendon moored submerged floating tunnel (SFT) due to tendon slack. In general, environmental loadings such as wave and current govern SFT design. Especially, the wave force, whose amplitude and direction continuously change, directly induces the dynamic behavior of the SFT. The motion of the floating tube, induced by the wave force, leads dynamic response of the attached tendons and the dynamic change of internal forces of the tendons significantly affects to the fatigue design as well as the structural strength design. When the severe motion of the SFT occurs due to significant waves, tendons might lose their tension and slack so that the floating tube can be transiently instable. In this study, the characteristics of dynamic instability of the SFT due to tendon slack are investigated performing hydrodynamic analysis. In addition, the effects of draft, buoyancy-weight ratio, and tendon inclination on tendon slack and dynamic instability behavior are analytically investigated.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.4
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• pp.71-80
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• 1990

Model tests for the ultimate pullout resistance of anchorages and investigation of failure behaviors in cohesionless soil have been conducted. The factors affecting the anchorage are mostly the geometry of the system, and soil properties of sands. The main conclusions of the experimental work were as follows. 1. The load - displacement relationship can be a form of parabolic curve for all plates. 2. The change in ultimate pullout resistance of anchor is mostly affected by embedment ratio and size of anchor, and influenced to a lesser degree by its shape. 3. Critical embedment ratio which is defined as the failure mode changes from shallow to deep mode is increased with increasing height of anchor. 4. For a constant anchor height, as the width of anchor increases the ultimate pullout resistance also increases. However, considering the efficiency of anchor for unit area, width of anchor does not appear to have any sigrnificant contribution on increasing anchor city. 5. Anchor capacity has a linear relation to sand density for any given section and the rate of change increases as the section increases. Critical depth determining the failure patterns of anchor is decreased with a decrease of sand density. 6. With increasing inclination angle, size of anchor, and decreasing embedment ratio, the ultimate pullout resistance of anchor under inclined loading is significantly decreased. 7. The ultimate pullout resistance of double anchor, a method of improving single of anchor capacity, is influenced by the center - to - center spacing adjacent anchors. It is also found that tandem and parallel anchor rigging arrangements decrease the anchor system capacity to less than twice the single anchor capacity due to anchor interference.

• Journal of Astronomy and Space Sciences
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• v.28 no.3
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• pp.203-216
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• 2011

To prepare for a future Korean lunar orbiter mission, semi-optimal lunar capture orbits using finite thrust are designed and analyzed. Finite burn delta-V losses during lunar capture sequence are also analyzed by comparing those with values derived with impulsive thrusts in previous research. To design a hypothetical lunar capture sequence, two different intermediate capture orbits having orbital periods of about 12 hours and 3.5 hours are assumed, and final mission operation orbit around the Moon is assumed to be 100 km altitude with 90 degree of inclination. For the performance of the on-board thruster, three different performances (150 N with $I_{sp}$ of 200 seconds, 300 N with $I_{sp}$ of 250 seconds, 450 N with $I_{sp}$ of 300 seconds) are assumed, to provide a broad range of estimates of delta-V losses. As expected, it is found that the finite burn-arc sweeps almost symmetric orbital portions with respect to the perilune vector to minimize the delta-Vs required to achieve the final orbit. In addition, a difference of up to about 2% delta-V can occur during the lunar capture sequences with the use of assumed engine configurations, compared to scenarios with impulsive thrust. However, these delta-V losses will differ for every assumed lunar explorer's on-board thrust capability. Therefore, at the early stage of mission planning, careful consideration must be made while estimating mission budgets, particularly if the preliminary mission studies were assumed using impulsive thrust. The results provided in this paper are expected to lead to further progress in the design field of Korea's lunar orbiter mission, particularly the lunar capture sequences using finite thrust.

• Korean Institute of Interior Design Journal
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• v.21 no.2
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• pp.92-100
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• 2012

This study was to examine the pattern of visual interpretation in the process of eye-tracking. I categorized the subjects' observation inclination for analysis so that I could find out which element the user observing the space concentrated and explored. First, for 2 minutes of observation, there occurred 171 times of eye-fixations and 9.8 times of observation frequency on average, which showed that the subject, through this observing fixation, spent 44.5% of the entire time performing the visual activity in order to acquire the "visual understanding" of the lobby-space. Second, I found out that there was a consistent observation type as the time passed. I could categorize the subjects observing the space into 6 concentrating types and 3 discontinuing ones of observation types, which category can be utilized as data for analyzing the subjects' characteristics at space-observation. Third, the type, which was so intensive as to get the visual understanding on the space, was mostly of the case that (1) the subject had a kind of high degree of observation type, exploring the space, again having high degree of the observation type [Type A], (2) the subject repeated the concentration from the early part to the latter [Type C], which can be considered to be the observation type generally shared. Fourth, in the case of observing the space, 45.8% of the subjects showed a high rate of concentration at the time of starting the observation and in less than two minutes. The subjects of type A can be considered to understand the space visually by distinctively repeating the concentration and exploration.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.3
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• pp.279-285
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• 2012

It is necessary to install the inert gas system(IGS) for preventing fire and explosion in LNGC main diesel engine crankcase besides oil mist detector(OMD) unit with $CO_2$ gas injector. Therefore, to design the liquid nitrogen IGS, analytical work is conducted for predicting the heat input load of liquid nitrogen heater with two-phase stratified flow model. This paper also presents the effects of changes in pipe diameter, saturated pressure, and inclination angle by ship's movement on cryogenic two-phase stratified flows. It is found that the stratified model gives reasonable predictions, and the model is effective to predict the heat input load of liquid nitrogen IGS.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.5
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• pp.219-227
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• 2016

As the largest source of food waste is housing, and the food waste properties are good enough to recycle, the proactive approach to conventional food waste disposal is highly regarded. This research is to examine food waste management in the Seoul Metropolitan Area (SMA) and non-SMA and to analyze the public inclination to disseminate zero-food waste system (ZFWS) with fermentation and extinction technology in multifamily housing estates. The self-administered questionnaire survey was conducted and the collected data were statistically analyzed. The main findings are summarized as follows: food waste in multifamily housing estates were retrieved by refuse truck and largely recycled for compost and forage. Also, many local governments were in favor of ZFWS, and unwilling to invest in it due to financial constraint. It's found that logistics of ZFWS is likely to be influenced by important features such as a considerable amount of cost saving, effective energy recovery, and efficient operation/management.

• Bulletin of the Korean Space Science Society
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• 2005.04a
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• pp.129-132
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• 2005

This paper describes BAUSAT-2 orbital thermal analysis and preliminary design of thermal control subsystem. To design thermal control subsystem of HAUSAT-2, we have considered active & passive thermal control method based on basic theory and themal equilibrium equation. Using this result, suitable thermal control method and material have been selected. We have designed thermal control subsystem based on analysis of HAUSAT-2's thermal environments on sun synchronous orbit with altitude 650km, inclination $98^{\circ}$ and thermal distribution and range expectation of each HAUSAT-2's surface. Thermal analysis consists of system level, box level and board level analysis. We have completed system level and box level analysis. Till now, board level analysis of main heat dissipation board in progress. Thermal control subsystem has designed according to thermal analysis result. This design is to maintain all of the HAUSAT-2 components within the allowable temperature limits. In future, STM

• Journal of Astronomy and Space Sciences
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• v.32 no.2
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• pp.127-136
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• 2015

We present a by-product of our long term photometric monitoring of cataclysmic variables. 2MASS J18024395 +4003309 = VSX J180243.9 +400331 was discovered in the field of the intermediate polar V1323 Her observed using the Korean 1-m telescope located at Mt. Lemmon, USA. An analysis of the two-color VR CCD observations of this variable covers all the phase intervals for the first time. The light curves show this object can be classified as an Algol-type variable with tidally distorted components, and an asymmetry of the maxima (the O'Connell effect). The periodogram analysis confirms the cycle numbering of Andronov et al. (2012) and for the initial approximation, the ephemeris is used as follows: Min I. BJD = 2456074.4904+0.3348837E. For phenomenological modeling, we used the trigonometric polynomial approximation of statistically optimal degree, and a recent method "NAV" ("New Algol Variable") using local specific shapes for the eclipse. Methodological aspects and estimates of the physical parameters based on analysis of phenomenological parameters are presented. As results of our phenomenological model, we obtained for the inclination $i=90^{\circ}$, $M_1=0.745M_{\odot}$, $M_2=0.854M_{\odot}$, $M=M_1+M_2=1.599M_{\odot}$, the orbital separation $a=1.65{\cdot}10^9m=2.37R_{\odot}$ and relative radii $r_1=R_1/a=0.314$ and $r_2=R_2/a=0.360$. These estimates may be used as preliminary starting values for further modeling using extended physical models based on the Wilson & Devinney (1971) code and it's extensions

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.73-81
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• 2018

The purpose of this study is to research the regulation of durability standard of underground structures monitoring sensors. The durability criteria for construction monitoring sensors of domestic construction companies, the standard years of contents such as buildings on the income tax implementation regulations, and the standards of the Public Procurement Service for construction monitoring and construction machinery were analyzed. The durability criterion on products such as the inclination meter and the strain gauge, which are purchased from the Public Procurement Service prior to installation on the underground structure, is 8 to 10 years. It is considered that the monitoring sensor installed in the paperboard and the concrete structure at the time of construction will have considerably shortened service life rather than the useful life of the product itself due to various adverse factors such as groundwater influence and compaction.